Pick-ups: Export button generates empty file

[emilyeros]

When exporting data for the pick up metric, an empty JSON file is generated. (This happens for bins and streets)

For drop-offs, exporting either the bins or the street segments actually exports the bins.

[morganherlocker]

(This happens for bins and streets)

See explanation here:

#32 (comment)

tldr: streets are not intended to be exposed through the UI yet, since they rely on a feature that has not been implemented yet. The bin part of this issue is a possible bug that needs review.

[morganherlocker]

This has been patched and tested. The issue was a typo.

cf58187